1. Field of the Invention
The present invention relates to a method and a system for controlling an outside incoming call transfer in a plurality of private branch exchanges (PBXs) which are network-connected via a communication network such as an ISDN (Integrated Service Digital Network).
2. Related Background Art
In general, a PBX refers to a system, which is installed on the premises of a company, a factory, a government office, a school, or the like, for controlling exchanges or connections between a plurality of accommodated extension terminals and between the extension terminals and external terminals (general telephone sets), thereby providing extension incoming calls or other services in its own system only on the premises.
In the PBXs accommodating a plurality of extension terminals as stated above, there is a known system having a function of operating a plurality of PBXs (hereinafter, each of the PBXs is simply referred to as a system, if necessary, in some cases) as if they were a single system by networking-connecting the plurality of PBXs (an intersystem communication) so that they can communicate with each other via a network such as the ISDN.
The system comprising the plurality of network-connected PBXs is generally provided with a function of originating a call from the other system accommodating an originating terminal to a transfer destination as an originating outside line for use in a transfer of an outside incoming call to a transfer destination preset in an incoming terminal (a transfer source terminal) when an extension terminal of a user's own system receives a call from an extension terminal (originating terminal) of the other system in the network-connected systems, if an incoming call transfer to an outside line is preset in the incoming terminal.
For example, if a system A is network-connected to a system B and a transfer source terminal having a preset incoming call transfer to an outside line of the system A receives a call from an originating terminal of the system B, the system B automatically originates a call of an outside call number (telephone number) to the transfer destination preset in the transfer source terminal so as to make outside calls via an outside incoming call transfer of the transfer source terminal between the originating terminal of the system B and the transfer destination.
On the other hand, there is, for example, the following conventional known technology regarding a transferred incoming call using an extension terminal accommodated in a PBX.
For example, there have been disclosed a call transfer system, which is capable of transferring an incoming call selectively for each incoming line, for reducing a period of time required for retrieving information on a transfer destination necessary for a call transfer and for improving a phone call handling service and an exchange unit for the call transfer system (for example, refer to JP-A-2000-92215). In this arrangement, an extension terminal previously registers information indicating extension terminals as transfer destinations on a transfer destination table, being associated with an extension number or a line of the terminal, for a PBX; and the PBX detects the extension number of the extension terminal that has requested a display of a transfer destination list, reads the transfer destination list information corresponding to the extension number, and notifies the extension terminal of the transfer destination list information.
Furthermore, there has been disclosed a PBX and a private automatic branch transfer method for decreasing wasteful transfers or inefficient call handling services (for example, refer to JP-A-2000-125017). In this arrangement, a memory unit stores transfer destination telephone numbers grouped by caller numbers on a table for each extension; a modem signal receiving circuit receives a caller number from a station line; a central control unit controls an automatic transfer operation; and the control is executed by selecting a transfer destination number corresponding to a caller number among received and stored caller numbers on the basis of the table data stored in the memory unit. With this arrangement, incoming calls are distributed to optimum transfer destinations according to callers when incoming extension terminals are unattended or the like.
Furthermore, there are a known telephone exchange unit and a known call transfer method for specifying transfer destinations separately according to types of incoming calls so that the calls can be transferred separately (for example, refer to JP-A-2001-197211). It is a telephone exchange unit accommodating a plurality of extension terminals and one or more outside lines and controlling incoming and outgoing call connections between extensions and between an extension and an outside line, comprising: transfer destination registration means for acquiring a transfer destination telephone number for an extension incoming call and that for an outside incoming call and registering the transfer destination telephone numbers being associated with telephone numbers related to a request for registering a transfer destination input from an extension telephone if the registration request is both for the extension incoming call and for the outside incoming call; and call processing means for performing transfer incoming call processing according to whether an incoming call is an extension incoming call or an outside incoming call by referring to the registration content when an extension telephone has received the incoming call.
Furthermore, there has been disclosed a private branch exchange system enabling a call to be transferred to a target transfer destination easily without effort (for example, refer to JP-A-1995-307802). It is an exchange system, which accommodates a plurality of extensions and outside lines, makes exchanges or connections between extensions and outside lines, and has a capability of transferring incoming calls between extensions using a transfer function, comprising: control means having a storing function of storing information of at least a relation between a source and a destination obtained at originating a call from an extension, a control function of obtaining information of an extension related to a source of originating an incoming call on the basis of the information stored by the storing function and controlling its display for an answering extension at transferring the incoming call from the extension answering the incoming call from an extension or an outside line to another extension, and a transfer function of performing a control so that the incoming call can be transferred to an extension corresponding to selection information on the basis of the selection information from the answering extension, wherein the extension is connected to a telephone terminal having means for displaying display information from the control means, operation means for selecting and operating one of the display information, and terminal control means for giving selection information obtained by the operation means to the control means.
In the conventional system comprising the plurality of PBXs network-connected as stated above, however, a call is originated from the other system accommodating an originating terminal to an outside line which is a transfer destination upon receiving an incoming call at a transfer source terminal having a setting of an outside incoming call transfer of a user's own system and thus an outside originating route of the transfer source terminal is not used, thereby causing the following problem.
For example, if a system A is network-connected to a system B, it is assumed that the system A is installed in Japan and the system B is installed in the US. In this condition, if a telephone number for accessing to areas in Japan is previously registered in an outside call transfer destination of an extension terminal accommodated in the system A and if a call is received by a terminal having a setting of an outside call transfer from the system B in the US to the system A in Japan, the call is originated with a telephone number for accessing to areas in Japan from the system B in the US. Therefore, when a telephone number of a transfer destination is sent to a station in the US, it causes incorrect dialing due to a difference in an area of the station problematically.
Regarding this, the conventional technologies of JP-A-2000-92215, JP-A-2000-125017, JP-A-2001-197211, and JP-A-1995-307802 stated above are not particularly intended for the outside incoming call transfer for a networking connection of a plurality of PBXs. Therefore, they cannot resolve the above problem.